The vapor compression type refrigeration cycle in which a fluid is cooled or heated by utilizing changes in the state of substances, namely evaporation and condensation, is widely used in heating and cooling equipment, refrigerators, hot water supply systems, and other equipment. For such vapor compression type refrigeration cycles, various working fluids including fluorocarbon refrigerants have been developed and put to use. Among them, HCFC22 (monochlorodifluoromethane) is widely used in heating and cooling equipment for air conditioning.
However, in recent years, the comprehension has arisen that the release of chlorofluorohydrocarbons into the atmosphere would destroy the ozone layer of the stratosphere to thereby exert an annihilating influence on the ecosystem of the earth, inclusive of the human race. For that reason, it has already been internationally stipulated that the use of those substances should be restricted and, in the future, totally prohibited. Under the circumstances, it is an urgent mission to develop novel refrigerants free of risks for destruction of the ozonosphere.
Accordingly, a number of nonazeotropic mixed refrigerants has been proposed recently in an attempt to make up for characteristics which cannot be provided by any single refrigerant by using a mixture of refrigerants (e.g. Japanese Unexamined Patent Publications Nos. 79288/1989 and 287688/1991 and Japanese Examined Patent Publication No. 55942/1994).
In a phase change such as evaporation or condensation, a nonazeotropic mixture tends to readily allow evaporation of a component having a lower boiling point and condensation of a high-boiling component and thus undergo changes in composition. This tendency is more pronounced in the case of evaporation, namely phase change from liquid to vapor. The greater the difference in boiling point between constituents of the mixture is, the more remarkable said tendency is. Therefore, when such a nonazeotropic mixture is transferred from one container to another, it is common practice to draw out the mixture from the liquid phase in order to avoid the phase change. However, even when the liquid phase is withdrawn, the resulting reduction in pressure or expansion of the gaseous phase causes evaporation of the lower-boiling component in the liquid phase. Where the difference in boiling point between the components of the mixture is great, a change in composition amounting to about several percent may readily result.
However, even when the change in composition is of the order of several percent, a marked change in refrigerant performance occurs, with a decrease in refrigerating capacity or efficiency and, in addition, the safety features of the refrigerant, for example the combustibility, are greatly influenced.
Therefore, there has been proposed a method for transfer-filling a nonazeotropic mixture without a compositional alteration that may arise from transfer-filling which method comprises drawing out, for transfer-filling into a second container, the liquid phase of a nonazeotropic mixture from a first container containing said mixture, under pressurization of said first container from the vapor phase side thereof using a low-boiling liquefied gas which is the lowest-boiling component of said nonazeotropic mixture or a mixture composed exclusively of the same liquefied gas components as those of said nonazeotropic mixture and having a vapor pressure corresponding to at least 1.1 times as high as the vapor pressure of said nonazeotropic mixture at 20.degree. C., or using a compressed gas (cf. Japanese Unexamined Patent Publication No. 4997/1996). However, this method is disadvantageous in that the proportion of the low-boiling component increases upon excessive pressurization with the low-boiling liquefied gas or compressed gas.